Engineering proteins that bind to cell surface carbohydrates.

Carbohydrate residues covalently linked to plasma membrane proteins and lipids often provide specific markers at the cell surface. Traditionally such carbohydrate structures have been identified using antibodies and lectins. However problems of affinity and lack of specificity have restricted their usefulness. Protein engineering offers a way round these difficulties. In the case of some specialised cell surface carbohydrate structures, such as polysialic acid, enzymes may be useful analytical tools. Endosialidases specific for polysialic acid have recently been cloned and sequenced.